using UnityEngine;
using System.Collections;

[AddComponentMenu("AQUAS/Reflection")]
[ExecuteInEditMode] // Make mirror live-update even when not in play mode
public class AQUAS_Reflection : MonoBehaviour
{
	public bool m_DisablePixelLights = true;
	public int m_TextureSize = 256;
	public float m_ClipPlaneOffset = 0.07f;
	
	public LayerMask m_ReflectLayers = -1;
	
	private Hashtable m_ReflectionCameras = new Hashtable(); // Camera -> Camera table
	
	private RenderTexture m_ReflectionTexture = null;
	private int m_OldReflectionTextureSize = 0;
	
	private static bool s_InsideRendering = false;

	public void OnWillRenderObject()
	{
		if( !enabled || !GetComponent<Renderer>() || !GetComponent<Renderer>().sharedMaterial || !GetComponent<Renderer>().enabled )
			return;
		
		Camera cam = Camera.current;
		if( !cam )
			return;
		
		// Safeguard from recursive reflections.        
		if( s_InsideRendering )
			return;
		s_InsideRendering = true;
		
		Camera reflectionCamera;
		CreateMirrorObjects( cam, out reflectionCamera );
		
		// find out the reflection plane: position and normal in world space
		Vector3 pos = transform.position;
		Vector3 normal = transform.up;
		
		// Optionally disable pixel lights for reflection
		int oldPixelLightCount = QualitySettings.pixelLightCount;
		if( m_DisablePixelLights )
			QualitySettings.pixelLightCount = 0;
		
		UpdateCameraModes( cam, reflectionCamera );
		
		// Render reflection
		// Reflect camera around reflection plane
		float d = -Vector3.Dot (normal, pos) - m_ClipPlaneOffset;
		Vector4 reflectionPlane = new Vector4 (normal.x, normal.y, normal.z, d);
		
		Matrix4x4 reflection = Matrix4x4.zero;
		CalculateReflectionMatrix (ref reflection, reflectionPlane);
		Vector3 oldpos = cam.transform.position;
		Vector3 newpos = reflection.MultiplyPoint( oldpos );
		reflectionCamera.worldToCameraMatrix = cam.worldToCameraMatrix * reflection;
		
		// Setup oblique projection matrix so that near plane is our reflection
		// plane. This way we clip everything below/above it for free.
		Vector4 clipPlane = CameraSpacePlane( reflectionCamera, pos, normal, 1.0f );
		Matrix4x4 projection = cam.projectionMatrix;
		CalculateObliqueMatrix (ref projection, clipPlane);
		reflectionCamera.projectionMatrix = projection;
		
		reflectionCamera.cullingMask = ~(1<<4) & m_ReflectLayers.value; // never render water layer
		reflectionCamera.targetTexture = m_ReflectionTexture;
		GL.invertCulling = true;
		reflectionCamera.transform.position = newpos;
		Vector3 euler = cam.transform.eulerAngles;
		reflectionCamera.transform.eulerAngles = new Vector3(0, euler.y, euler.z);
		reflectionCamera.Render();
		reflectionCamera.transform.position = oldpos;
		GL.invertCulling = false;
		Material[] materials = GetComponent<Renderer>().sharedMaterials;
		foreach( Material mat in materials ) {
			if( mat.HasProperty("_ReflectionTex") )
				mat.SetTexture( "_ReflectionTex", m_ReflectionTexture );
		}
		
		// Set matrix on the shader that transforms UVs from object space into screen
		// space. We want to just project reflection texture on screen.
		Matrix4x4 scaleOffset = Matrix4x4.TRS(
			new Vector3(0.5f,0.5f,0.5f), Quaternion.identity, new Vector3(0.5f,0.5f,0.5f) );
		Vector3 scale = transform.lossyScale;
		Matrix4x4 mtx = transform.localToWorldMatrix * Matrix4x4.Scale( new Vector3(1.0f/scale.x, 1.0f/scale.y, 1.0f/scale.z) );
		mtx = scaleOffset * cam.projectionMatrix * cam.worldToCameraMatrix * mtx;
		foreach( Material mat in materials ) {
			mat.SetMatrix( "_ProjMatrix", mtx );
		}
		
		// Restore pixel light count
		if( m_DisablePixelLights )
			QualitySettings.pixelLightCount = oldPixelLightCount;
		
		s_InsideRendering = false;
	}
	
	
	// Cleanup all the objects we possibly have created
	void OnDisable()
	{
		if( m_ReflectionTexture ) {
			DestroyImmediate( m_ReflectionTexture );
			m_ReflectionTexture = null;
		}
		foreach( DictionaryEntry kvp in m_ReflectionCameras )
			DestroyImmediate( ((Camera)kvp.Value).gameObject );
		m_ReflectionCameras.Clear();
	}
	
	
	private void UpdateCameraModes( Camera src, Camera dest )
	{
		if( dest == null )
			return;
		// set camera to clear the same way as current camera
		dest.clearFlags = src.clearFlags;
		dest.backgroundColor = src.backgroundColor;        
		if( src.clearFlags == CameraClearFlags.Skybox )
		{
			Skybox sky = src.GetComponent(typeof(Skybox)) as Skybox;
			Skybox mysky = dest.GetComponent(typeof(Skybox)) as Skybox;
			if( !sky || !sky.material )
			{
				mysky.enabled = false;
			}
			else
			{
				mysky.enabled = true;
				mysky.material = sky.material;
			}
		}
		// update other values to match current camera.
		// even if we are supplying custom camera&projection matrices,
		// some of values are used elsewhere (e.g. skybox uses far plane)
		dest.farClipPlane = src.farClipPlane;
		dest.nearClipPlane = src.nearClipPlane;
		dest.orthographic = src.orthographic;
		dest.fieldOfView = src.fieldOfView;
		dest.aspect = src.aspect;
		dest.orthographicSize = src.orthographicSize;
	}
	
	// On-demand create any objects we need
	private void CreateMirrorObjects( Camera currentCamera, out Camera reflectionCamera )
	{
		reflectionCamera = null;
		
		// Reflection render texture
		if( !m_ReflectionTexture || m_OldReflectionTextureSize != m_TextureSize )
		{
			if( m_ReflectionTexture )
				DestroyImmediate( m_ReflectionTexture );
			m_ReflectionTexture = new RenderTexture( m_TextureSize, m_TextureSize, 16 );
			m_ReflectionTexture.name = "__MirrorReflection" + GetInstanceID();
			m_ReflectionTexture.isPowerOfTwo = true;
			m_ReflectionTexture.hideFlags = HideFlags.DontSave;
			m_OldReflectionTextureSize = m_TextureSize;
		}
		
		// Camera for reflection
		reflectionCamera = m_ReflectionCameras[currentCamera] as Camera;
		if( !reflectionCamera ) // catch both not-in-dictionary and in-dictionary-but-deleted-GO
		{
			GameObject go = new GameObject( "Mirror Refl Camera id" + GetInstanceID() + " for " + currentCamera.GetInstanceID(), typeof(Camera), typeof(Skybox) );
			reflectionCamera = go.GetComponent<Camera>();
			reflectionCamera.enabled = false;
			reflectionCamera.transform.position = transform.position;
			reflectionCamera.transform.rotation = transform.rotation;
			reflectionCamera.gameObject.AddComponent<FlareLayer>();
			go.hideFlags = HideFlags.HideAndDontSave;
			m_ReflectionCameras[currentCamera] = reflectionCamera;
		}        
	}
	
	// Extended sign: returns -1, 0 or 1 based on sign of a
	private static float sgn(float a)
	{
		if (a > 0.0f) return 1.0f;
		if (a < 0.0f) return -1.0f;
		return 0.0f;
	}
	
	// Given position/normal of the plane, calculates plane in camera space.
	private Vector4 CameraSpacePlane (Camera cam, Vector3 pos, Vector3 normal, float sideSign)
	{
		Vector3 offsetPos = pos + normal * m_ClipPlaneOffset;
		Matrix4x4 m = cam.worldToCameraMatrix;
		Vector3 cpos = m.MultiplyPoint( offsetPos );
		Vector3 cnormal = m.MultiplyVector( normal ).normalized * sideSign;
		return new Vector4( cnormal.x, cnormal.y, cnormal.z, -Vector3.Dot(cpos,cnormal) );
	}
	
	// Adjusts the given projection matrix so that near plane is the given clipPlane
	// clipPlane is given in camera space. See article in Game Programming Gems 5 and
	// http://aras-p.info/texts/obliqueortho.html
	private static void CalculateObliqueMatrix (ref Matrix4x4 projection, Vector4 clipPlane)
	{
		Vector4 q = projection.inverse * new Vector4(
			sgn(clipPlane.x),
			sgn(clipPlane.y),
			1.0f,
			1.0f
			);
		Vector4 c = clipPlane * (2.0F / (Vector4.Dot (clipPlane, q)));
		// third row = clip plane - fourth row
		projection[2] = c.x - projection[3];
		projection[6] = c.y - projection[7];
		projection[10] = c.z - projection[11];
		projection[14] = c.w - projection[15];
	}
	
	// Calculates reflection matrix around the given plane
	private static void CalculateReflectionMatrix (ref Matrix4x4 reflectionMat, Vector4 plane)
	{
		reflectionMat.m00 = (1F - 2F*plane[0]*plane[0]);
		reflectionMat.m01 = (   - 2F*plane[0]*plane[1]);
		reflectionMat.m02 = (   - 2F*plane[0]*plane[2]);
		reflectionMat.m03 = (   - 2F*plane[3]*plane[0]);
		
		reflectionMat.m10 = (   - 2F*plane[1]*plane[0]);
		reflectionMat.m11 = (1F - 2F*plane[1]*plane[1]);
		reflectionMat.m12 = (   - 2F*plane[1]*plane[2]);
		reflectionMat.m13 = (   - 2F*plane[3]*plane[1]);
		
		reflectionMat.m20 = (   - 2F*plane[2]*plane[0]);
		reflectionMat.m21 = (   - 2F*plane[2]*plane[1]);
		reflectionMat.m22 = (1F - 2F*plane[2]*plane[2]);
		reflectionMat.m23 = (   - 2F*plane[3]*plane[2]);
		
		reflectionMat.m30 = 0F;
		reflectionMat.m31 = 0F;
		reflectionMat.m32 = 0F;
		reflectionMat.m33 = 1F;
	}
}
